While Trump has disputed reports about claims by former FBI director James Comey — who told the Senate last week he believes Trump fired him because he refused to drop the Russia investigation — the president has also tried to shift the focus to Comey's criticism of Lynch.

"A.G. Lynch made law enforcement decisions for political purposes ... gave Hillary Clinton a free pass and protection. Totally illegal!" Trump tweeted.

Trump took to social media just hours before Attorney General Jeff Sessions testifies before the Senate Intelligence Committee, a session likely to touch on an investigation of possible links between Trump's campaign and Russians who sought to interfere in last year's election.

A.G. Lynch made law enforcement decisions for political purposes...gave Hillary Clinton a free pass and protection. Totally illegal!